Modern MEMS sensors for measuring inertial quantities, such as acceleration, rate of rotation, etc., are made up of one or more micromechanical structures made of silicon (referred to herein as sensor cores) and an evaluation electronics unit.
For the example of an acceleration sensor, the named sensor cores are essentially made up of a seismic mass suspended centrally on a spring, having electrode fingers and fixed electrodes that are immovably anchored. The seismic mass is at electrical potential CM, and the fixed electrodes are at potential C1 or C2. Between CM and C1, and between CM and C2, a capacitance forms that changes when an external acceleration is applied, because the seismic mass is deflected and the distance of the movable fingers from the fixed electrodes becomes greater or smaller. This change in capacitance can be measured in an evaluation circuit, and the applied acceleration can be calculated from this.
EP 0 773 443 B1 discloses a micromechanical acceleration sensor.